Polar Kerr rotation in light rare earth R 2Fe 14B compounds

Abstract

The wavelength dependence of the polar Kerr rotation angle at room temperature ( θ K) in the tetragonal R 2Fe 14B compounds, where R = Ce, Pr, Nd, Sm and Y, has been measured. θ K reaches −0.47° in Nd 2Fe 14B for λ = 800 nm. The rare earth contribution to the Kerr rotation is detected in the short-wavelength range between 250 nm (the lower limit of the measuring system) and about 450 nm through a systematic variation of the peak position toward long wavelengths with increasing atomic number of the rare earth. From the absence of the 4f-electron contributions to θ K in Ce 2Fe 14B, it is concluded that Ce has no 4f moment.